ElDude, there's something about Sins that makes it more difficult to begin with than most other similar games. I lost my first three or four games to an easy AI. Here are a few tips:
Remember that your first capital ship is free. Build the one that can also colonise planets; it'll save a bit on resources in the early game. Send it on its own to planets that have, say, five or fewer defenders. Don't let it colonise the planet until the siege ships have been taken out.
People may disagree, but in my opinion the weapon/shield/armour upgrades are less important in the early game. Concentrate on maximising your resource output (non-combat tech tree), build up your fleet caps, and build up your fleets. Swarms of frigates are very powerful in the early game.
When you really start to expand, start climbing the tech tree that gives you your starbases and hangars. Personally I find that a full load of hangar defenses are the best way to protect a planet in early-middle game. Starbases cost a lot but, when upgraded at least a few times, are absolutely superb at defending worlds.
Play a 2v2 with locked teams - you and an AI against two other AIs, all of the same difficulty level. This will create a bigger, longer game while giving you breathing room.
Use the black market! If you gain a resource edge, you can then use the market to make a good deal of cash too.
I could post more but that should get you started. Good luck!